Redis

Redis (Remote Dictionary Server) is an open-source in-memory storage, used as a distributed, in-memory key–value database, cache and message broker, with optional durability. Because it holds all data in memory and because of its design, Redis offers low-latency reads and writes, making it particularly suitable for use cases that require a cache. Redis is the most popular NoSQL database, and one of the most popular databases overall.

This notebook goes over how to use Redis to store chat message history.

Setup

First we need to install dependencies, and start a redis instance using commands like: redis-server.

pip install -U langchain-community redis

from langchain_community.chat_message_histories import RedisChatMessageHistory

API Reference:

• RedisChatMessageHistory

Store and Retrieve Messages

history = RedisChatMessageHistory("foo", url="redis://localhost:6379")

history.add_user_message("hi!")

history.add_ai_message("whats up?")

history.messages

[HumanMessage(content='hi!'), AIMessage(content='whats up?')]

Using in the Chains

pip install -U langchain-openai

from typing import Optional

from langchain_core.prompts import ChatPromptTemplate, MessagesPlaceholder
from langchain_core.runnables.history import RunnableWithMessageHistory
from langchain_openai import ChatOpenAI

API Reference:

• ChatPromptTemplate
• MessagesPlaceholder
• RunnableWithMessageHistory
• ChatOpenAI

prompt = ChatPromptTemplate.from_messages(
    [
        ("system", "You're an assistant。"),
        MessagesPlaceholder(variable_name="history"),
        ("human", "{question}"),
    ]
)

chain = prompt | ChatOpenAI()

chain_with_history = RunnableWithMessageHistory(
    chain,
    lambda session_id: RedisChatMessageHistory(
        session_id, url="redis://localhost:6379"
    ),
    input_messages_key="question",
    history_messages_key="history",
)

config = {"configurable": {"session_id": "foo"}}

chain_with_history.invoke({"question": "Hi! I'm bob"}, config=config)

chain_with_history.invoke({"question": "Whats my name"}, config=config)

AIMessage(content='Your name is Bob, as you mentioned earlier. Is there anything specific you would like assistance with, Bob?')